Fig. 5. Cycloheximide does not affect bristle growth but does promote premature bundle breakdown. (a) A group of same-age thoraces (dissected from a single cohort of pupae 36 hours after puparium formation) were divided into two groups and cultured in the presence or in the absence (control) of 1 µM cycloheximide for 5 hours. Bristle lengths were measured from confocal images of phalloidin-stained microchaetes. Bristle length was unaffected when cultured in cycloheximide. (b) A group of same-age thoraces (dissected from a single cohort of pupae 42 hours after puparium formation) were divided into two groups and cultured in the presence or in the absence (control) of 1 µM cycloheximide for two hours. Actin bundles were imaged by confocal microscopy and evaluated by the criteria illustrated in Fig. 1. A total of 56 bristles were examined and the percentages of bristles exhibiting tapering modules or bundle ghosts characteristic of depolymerizing bundles are presented. Of interest here is that cycloheximide promotes the breakdown of modules usually seen in older bristles (e.g., Fig. 1).